Fluid pressure operated brake



June 30, 1936. BQWEN Re. 20,021

FLUID PRESSURE OPERATED BRAKE MECHANISM Original Filed Aug. 18, 1.928 2Sheets-Sheet l i if i Y i v i H z I E firfierf'jazaezz 2 Sheets-Sheet 2w w M I:

H. C. BOWEN FLU ID PRESSURE OPERATED BRAKE MECHANISM Jun 30, 1936.

Reissued June 30, 1936 PATENT OFFICE FLUID PRESSURE orEnATEn BRAKEMECHANISM Herbert G. Bowen, Detroit, Mich., assignor to Hydraulic BrakeCompany, Detroit, Mich., a corporation of California Original No.1,886,936, dated November 8, 1932,

Serial No. 300,407, August 18, 1928. Application for reissue May 11,1933, Serial No. 670,596

20 Claims. (01. 188-152) This invention relates to a fluid pressureoperated brake mechanism, and more particularly to a device for applyingan initial pressure to a fluid operated brake system prior to theapplication of. the brake operating pressure.

In fluid pressure operated brake systems there is frequently a lostmotion between the pressure applying device and the brakes due in partto a loose fit or play between the mechanically interconnected parts andto the clearance between the brake shoes and drums when the brake shoesare retracted from the drums, which often results in a considerabiemovement of the pressure applying device before the. brakes becomeeffective.

An object of the invention is to provide an apparatus for applying aninitial pressure to the fluid pressure operated system prior to theapplication of the brake operating pressure to remove the slacktherefrom.

A further object of the invention is to provide a slack remover operableby energy received from the manifold of the motor for propelling a motorvehicle.

Other objects and advantages of the invention will appear as thedescription proceeds.

A complete understanding of the invention may be had by reference to thefollowing description taken in conjunction with the accompanyindrawings, in which Fig. 1 represents schematically an apparatusembodying the invention for applying the brakes in a fluid pressureoperated brake system;

Fig. 2 is a cross sectional view of the cylinder for applying theinitial slack removing pressure to the system;

Fig. 3 is a cross sectional view of a fluid pressure actuated cylinderfor operating the initial pressure cylinder shown in Fig. 2;

' Fig. 4 is a cross sectional view taken on lines 8-4 of Fig. 2, and

Fig. 5 is a cross sectional view taken on the lines 5-5 of Fig. 2.

Referring to the drawings, and more particularly to Fig. 1, apluralityof brake mechanisms 8 are actuated by the pressure produced ina master cylinder I. Each brake mechanism may comprise brake shoes 6apivoted at El; on a supporting pan 6c and actuated by pistons Ed in acylinder 6e 7 .to engage the drum 6f from which the brake shoes areretracted by spring By. The specific structure of the brake mechanismsforms no part of my invention and it' is to be understood that otherbrake mechanisms than that. illustrated may be utilized in a. brakingsystem. embodying my invention. The master cylinder I is operated by apinion 22.

lever 8 which is connected through a link 8 to a manually operable pedalII and serves to reciprocate a piston l2 within the master cylinder I tocommunicate a pressure through a tube I to the brakes 6.

A secondary cylinder I3 is also connected through the tube III to thepressure system and has a. piston I4 reciprocally mounted therein.Attached to the piston I4 is a threaded piston rod I which is slidablymounted in a bearing cap l6 having an upper bearing I1 and a lowerbearing I8. The piston rod I5 is provided with a longitudinal groove I9into which a projection 2| of the upper bearing II extends for thepurpose of allowing longitudinal movement of the piston rod andpreventing rotative movement thereof.

A pinion 22 is supported between the bearings l1 and I8 and is providedwith an internal thread which engages the threads of the piston rod I5.The threads of the piston rod I5 and the pinion 22 are of such a pitchthat the connection is irreversible; that is, a rotation of the pinion22- will cause a longitudinal movement of the piston rod I5, but alongitudinal force exerted upon the piston rod I5 will not cause arotation of the In order to rotate the pinion 22 ,a rack 23 is held inengagement therewith by a support 24 integral with the bearing cap l6.

The rack 23 is formed integral with a piston rod 25 which is attached tothe piston 26 reciprocally mounted in a cylinder 21. Supported on theupper portion of the cylinder 21 is a valve mechanism 28 having a doublevalve 29 which may be engaged with either the valve seat 3| or thevalveseat 32.

A valve stem 33 for operating the valve extends from the valve mechanismand contacts with the lever 8 which holds the valve 29 in engagementwith the seat 3| when the lever B is in its inoper ative position, inwhich position of the valve the cylinder 21 is connected through a duct35 to a plurality of ports 38 leading to the atmosphere. Upon a. slightmovement of the lever 8 a spring 34 will shift the valve 29 intoengagement with the valve seat 32, in which'position of the valve thecylinder 21 will be connected through the duct 35 to a tube 36 leadingto themanifold 36' of the vehicle motor.

The operation of-the apparatus is as follows: v

rotation of the pinion 22 through the rack 23 and g to the manifold ofthe motor vehicle in which the operation of the motor constantlymaintains a vacuum.

The vacuum thus applied to the cylinder 21 tends to withdraw the airtherefrom and allows the atmospheric pressure to force the piston 26into the cylinder 21 against the action of a spring The movement of thepiston 26 causes the engage the brake shoes with the drums but withcylinder.

insufllcient force to produce a braking effect. At this time the lever 8will have moved only far enough to operate the valve 29. As the pressurein the system increases, due to the continued movement ,of the lever Bin applying the brakes, the piston M will not be forced upwardly onaccount of the irreversible connection between the piston rod l5 and thepinion 22.

The initial pressure produced in the cylinder l3 therefore remainseffective during the entire braking process, and the piston I4 is notwithdrawn until the lever B resumes its normal position and moves thevalve 29 to its right hand position.

When the valve 29 is returned to its right-hand.

position, the cylinder 21 is connected through duct 35 and ports '38 tothe atmosphere, allowing the spring 31 to move the piston 26 outwardlyuntil it engages the bearing 39, which limits its outward movement,restoring the piston I4 in the cylinder I 3 to its normal position.

It will be seen, therefore, that the apparatus serves to apply aninitial pressure to the fluid pressure system and retain thatpressure'during the entire braking process.

The embodiment of the invention herein described and illustrated ismerely a convenient and useful form of the invention which is capable.of many other modifications without departing from the spirit and scopeof the invention, which is to be limited only by the scope of theappended claims.

Iclaim:

1. The combination in a fluid pressure oper ated brake system, of meansfor producing a pres- 2. In a fluid pressure operated brake system, amaster cylinder and piston, means for actuating the pistonof the mastercylinder to produce a pressure in the system, and fluid pressureactuated means responsive to the initial movement of said actuatingmeans for removing the slack from the brake system. a

3. In a fluid pressure operated'brake system, means for producing afluid pressure in the system, means movable to actuate the pressureproducing means, and fluid pressure actuated means responsive to theinitial movement of the movable means to remove the slack from thesystem.

4. In a fluid pressure operated brake system, a slack remover comprisinga cylinder, a piston in said cylinder, and an irreversible drivingconnection for movingthe piston in the cylinder to remove the slack fromthe system.

5. In a fluid pressure operated brake system, a. slack removercomprising a cylinder, a piston in said cylinder, a threaded piston rodfor moving the cylinder, a rotatable threaded member enthe secondarycylinder piston,

pressure means for rotating said rotatable mem- 6. The combination in afluid operated system, a main pressure means, a secondary pressuremeans, fluid pressure actuated means for completely operating thesecondary pressure means upon a partial operation of the main pressuremeans, and means for causing the secondary pressure means to remain inits operated position until the main pressure means has returned tonormal position.

'7. The combination in'a fluid pressure operated system, a mastercylinder having a piston, means for operating the piston of the mastercylinder, a secondary cylinder having a piston, and means for operatingthe piston of the secondary cylinder comprising a fluid operatedcylinder, and means for connecting said fluid operated cylinder to asource of energy upon a slight movement of the means for operating thepiston of the master tion until the means for operating the piston ofthe master cylinder has returned'to normal position.

9. The combination in a fluid pressure operated brake system, a mastercylinder, a pistontherefor, means for actuating said piston to produce abrake operating fluid pressure in the brake system, a secondarycylinder, a piston in said secondary cylinder, a threaded piston rodattached to an internally threaded pinion engaging said threaded pistonrod, a pressure actuated cylinder having a piston therein, a piston rodtherefor adapted to rotate said pinion, and means for producing anoperating pressure in the pressure cylinder upon a movement of the meansfor actuating the piston of the master cylinder whereby the secondarycylinder is caused to produce a slack removing pressure in the brakesystem prior to the brake operating pressure.

10. The combination in a fluid pressure operated brakesystem, a mastercylinder, a piston therefor, means for actuating said piston to producea brake operating pressure-in the system, a

secondary cylinder, a piston therefor, a threaded piston rod attached tosaid piston, an internally threaded pinion engaging the threaded pistonrod, a fluid pressure operated cylinder, a piston therefor, a piston rodattached to said last mentioned piston adapted upon its movement torotate said pinion, means including a valve for connecting the pressureoperated cylinder to a source of low pressure, and means for operatingsaid valve upon the initial movement of the means for actuating thepiston of the master cylinder whereby the pressure operated cylindercauses the secondary cylinder to produce a slack removing pressure inthe system prior to the brake operating pressure.

operably connected with the piston in said secondary cylinder whereby itis moved its full amount coordinately with the partial movement of thepiston in said master cylinder, and means means, disengageable from saidsecondary pressure means upon a partial operation of the main pressuremeans whereby the said secondary pressure means is completely operated.

13. In brake apparatus, an operator, a brake,

fa connection between said operator and said brake, means responsive tothe initial movement of said operator for varying the effective lengthof the connection between said operator and said brake to take up theslack in said connection and in said brake without correspondingmovement of said operator, said means comprising a source of suction, avacuum motor, a conduit extending from said source of suction to saidmotor, a valve in said conduit, and a connection from said operator tosaid valve.

14. In brake apparatus, an operator, a brake, a connection between saidoperator and said brake, means responsive to the initial movement ofsaid operator. for varying the eifective length of the connectionbetween said operator and said brake to take up the slack in saidconnection and in said brake without corresponding movement of saidoperator.

15. A hydraulic brake system comprising a brake pedal, brake shoes,means comprising a power device for taking up the clearance of the.

master cylinder, lines connecting said master cylinder and said wheelcylinder, a power slack' take-up device operated by initial movement ofthe brake pedal to produce pressure in the lines sufllcient to take up.the 'shoe clearance, and a piston in the master cylinder operated byfurther movement of the pedal which after the slack take-up -willproduce braking pressures in the lines without assistance from the powerdevice.

. 17. In brake apparatus using fluid and having a rotatable frictionelement and a cooperating friction elementadapted to be anchored againstmovement and adapted to be brought into contact with said rotatablefriction element for retarding movement of said rotatable frictionelement, means responsive to fluid pressure for moving said cooperatingelement into contact with said rotatable element, power operated meansfor applying pressure to said fluid solely for the purpose of removingall slack from said brake apparatus regardless of the condition of wearthereof, and additional means for applying higher pressures to saidfluid for urging said cooperating element into closer contact with saidrotatable element.

18. In hydraulic brake apparatus using a hydraulic fluid and having arotatable friction element and a cooperating friction element adapted toanchor against movement and adapted to be brought into contact with saidrotatable friction element for retarding movement of said rotatablefriction element, means responsive to fluid pressure for moving saidcooperating element into contact with said rotatable element, avacuumoperated power motor for applying non-braking pressures to saidfluid, and additional means for applying braking pressures to saidfluid.

l9. Thercombination with brake mechanism including a rotatable frictionelement, an anchored friction element, and an operating cylinder forsaid last-named element, of a master cylinder, a piston in saidcylinder, connections between said master cylinder and said operating 1cylinder, means comprising a vacuum cylinder for creating non-brakingpressures in the operating cylinder and for applying the anchoredfriction element to the rotatable friction e'lement, andmanually-operated means including the piston for creating brakingpressures in the operating cylinder and for forcing the anchoredfriction element more tightly against the rotatable friction. element. I

20. In brake apparatus of'the class described, the combination of anoperator, a brake drum, .a brake element adapted to be moved into engagepment with said drum, a fixed anchor for said brake element, aconnection between said operator and said brake element, meansresponsive to the initial movement-of said operator' for varying theeffective length of the connection between said operator and saidelement to move said element into engagement with said drum withoutcorresponding movement oif said operator.

HERBERT C. BOWEN.

